Shelf



FIG. 1 is a top, front and right side perspective view of a shelf showing my new design;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a front side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a rear elevational view thereof. 

The ornamental design of a shelf, as shown and described. 